1. Field of the Invention
This invention relates to agitating elements for washing machines of the type employing vertical axis agitators formed with unidirectionally-rotating auger portions combined with oscillating skirt portions to provide toroidal movement to the items within the tube of the machine.
2. Description of the Prior Art
It is recognized in the art that a so-called rollover or toroidal movement of fabric such as clothing being washed in a washer is required for uniform washability of loads, and especially for large loads. Such toroidal movement or roll-over consists of movement of the contents of the machine downwardly along the agitator barrel generally parallel to the agitator axis, radially outwardly along the agitator skirt and scrubbing vanes, upwardly along the peripheral wall of the basket, and radially inwardly near the surface of the wash liquid towards the agitator barrel. Good roll-over contributes significantly to good washability and uniformity of washing results.
Agitators which oscillate but which include a helically-vaned member or auger rotating stepwise in a single direction have been found to produce very good roll-over. Such agitators employ an oscillating agitator component having vanes which are symmetrical about a plane passing through the vane and the axis of the agitator, and due to this symmetry (and ignoring the acceleration characteristics of the means for oscillating the agitator), each half stroke of the oscillating agitator component has an equal tendency to rotate the clothes load in the basket. The net result then is that the stroke halves cancel each other in regard to angular rotation of the load. In the conventional agitator, which acts as one piece, this net zero rotation of the clothes load is desirable for producing minimum tangling of the load.
However, in double acting auger agitators employing a unidirectional auger in addition to the oscillating agitator component it has been found that there is a tendency of the auger element to drag the clothes load around in the direction of rotation of the auger element. Experience indicates that this rotation of the load caused by the unidirectional auger contributes heavily to tangling of the load. Load tangling, in turn, leads to high agitator shaft torque, high motor wattage, unbalanced spin loads and unloading problems. Such tangling may also reduce washability and uniformity of washing results, and may even result in damage to the fabrics. Thus, a problem encountered with such agitators has been a tendency toward rotation of the clothes load about the axis of the agitator causing objectionable tangling of clothes within the basket during the washing cycle.
Tangling may be minimized, however, by substantially minimizing rotation of the clothing load about the axis of the agitator. Some opposition to, or counter-action of, such rotation of the basket contents by the auger may be had by varying or adjusting to the clockwise versus the counterclockwise stroke or acceleration characteristics of an oscillating skirt portion of the agitator carrying flat, symmetric vanes. However, such measures are not generally sufficient to overcome the objectionable degree of rotation which can be induced by the auger.
There are many different examples of oscillating agitators in the prior art, and such agitators utilize a variety of different surface configurations. For example, the patent to Graham et al, U.S. Pat. No. 1,665,959, discloses an oscillating agitator element including generally ramp-like surfaces provided with ribs for scrubbing in response to agitator movement in one direction and side surfaces for redistributing the tub contents in response to agitator movement in the opposite direction.
The concept of an oscillating agitator including a unidirectionally-rotating auger is disclosed and claimed in patents assigned to the assignee of the present invention, specifically U.S. Pat. Nos. 3,987,508 (Platt), 3,987,651 (Platt), 3,987,652 (Ruble). However, these structures have not employed the asymmetric scrubbing vanes of the present invention to affect or decrease the net rotation of basket contents about the axis of the agitator caused by the auger.